A Comparative Study of Voltage Gain Tolerance in Conventional and Three-Level LLC Converters Against Circuit Variation

Hiroyuki Haga, Hidenori Maruta, Fujio Kurokawa

Abstract

This paper clarifies the relationship between voltage gain tolerance and normalized design parameters against resonant circuit components variation for mass production of LLC converters and three-level LLC converters. The LLC converter is an attractive solution for high power application, hence many photovoltaic systems which use LLC converter have been proposed. The multi-level LLC converter is also proposed to overcome a drawback of the conventional LLC converter. It is important on mass production stage to clarify the relationship between its voltage gain tolerance and design parameters against resonant circuit component variations, however it has rarely studied. Therefore, we study the relationship between voltage gain tolerance and three normalized design parameters related to the resonant circuit with Monte Carlo simulation. As a result, it has found that a conventional LLC converter and a three-level LLC converter have approximately same voltage gain tolerance characteristics. However the three-level LLC converter has a superior performance compared to the conventional LLC converter in aspect of the voltage gain tolerance. The reason for a difference of the performance comes from a design constraint. By utilizing this knowledge, designers can reduce unnecessary losses of the conventional and the three-level LLC converter which are generated by too much voltage gain margin; therefore this paper can contribute to improving performance in renewable energy generation systems.